Albert Einstein's best known equation: E=mc˛, published in the fourth of a series of papers that shook the foundations of physics in 1905, E=mc˛ is now linked with the power of the atom bomb.

The equation was final proof of the genius and imagination of the young German-born scientist who had yet to land a university post. The simple three letters standing for energy, mass, and the speed of light, encapsulated the idea that as you accelerate an object, it not only gets faster, it also gets heavier. That in turn makes further pushing less fruitful so that eventually nothing can be accelerated beyond the speed of light. The equation rounded out the theory of relativity he had started earlier in the year. Einstein soon recognised through the equation that the energy released in radioactivity - a phenomenon hardly understood at the time - might lead to measurable changes in mass. That idea was eventually to be translated into the physics of the atom bomb.

Whoops forgot… September 27 marked the centennial of the most famous equation in the world: E=mc˛. On that day in 1905, Albert Einstein submitted the paper that laid out the formula.

The original manuscript of a paper Albert Einstein published in 1925 has been found in the archives of Leiden University's Lorentz Institute for Theoretical Physics. The German-language manuscript is titled "Quantum theory of the monatomic ideal gas," and is dated December 1924. It is considered one of Einstein's last great breakthroughs. High-resolution photographs of the 16-page manuscript are posted on the institute's web site.